Try Google or Yahoo.
There is small possibility that buyer has wrote Your name in credits.

I have found few Youtube videos with my music, because buyer wrote link to my profile in video description.
And when You will try to search, don’t put in search field only Your AJ name, add song name to. it can help You to find something.

Sadly, no.
You can try to use some web services like tunesat.com (when it works…. I’ve been trying to login for 5 days but it seems to be offline). Otherwise, is just up to the purchaser to let you know if and where your music has been used.
Best,
Pietro